The invention relates to devices and methods for coating one or more yarns by a vapor deposition method.
Ceramic matrix composite (CMC) materials are used at operating temperatures that are relatively high. Such materials comprise fiber reinforcement made up of yarns of ceramic or carbon materials present within a ceramic matrix.
While making parts out of CMC, a fiber texture that is to form the fiber reinforcement of the part may initially be obtained, e.g. by three-dimensional weaving. The fiber texture is then shaped in order to obtain a fiber preform having a shape that is close to the shape of the part that is to be fabricated. The preform is then densified in order to form the matrix and thus obtain the final part, with the matrix being made by way of example in full or in part by a chemical vapor infiltration (CVI) method or by a melt infiltration (MI) MI method, for example. Prior to the textile forming step (weaving, braiding, . . . ), the yarns may have been coated in an interphase coating serving to slow down rupture of the fibers of the yarns by cracks that start initially within the matrix. By way of example, the embrittlement-release interphase coating may be made of a material of lamellar structure that, on a crack reaching the interphase, is capable of dissipating the cracking energy by localized un-bonding at atomic scale so that the crack is deflected within the interphase. By way of example, materials constituting the embrittlement-release interphase may be pyrolytic carbon (PyC), and boron nitride (BN), which present a lamellar structure. By way of example, the interphase coating may be formed by chemical vapor deposition (CVD), by chemical vapor infiltration (CVI), or indeed by a liquid technique.
Devices suitable for continuously coating a plurality of yarns with an interphase by chemical vapor deposition are proposed in the literature. Such devices may include a treatment chamber through which a plurality of yarns for coating are transported by being driven by a pulley system. A reactive gas mixture is injected into the treatment chamber via an inlet orifice in order to form the interphase coating on the yarns by chemical vapor deposition. Any reactive gas mixture that has not reacted, together with by-products of the reaction are pumped out via an outlet orifice that is offset from the inlet orifice along the longitudinal axis of the treatment chamber. In such devices, the injected gas mixture flows along the longitudinal axis of the treatment chamber until it is pumped out through the outlet orifice. Multilayer interphase coatings can be made by placing a plurality of units of this type in series each including a device for injecting a gas phase and a device for removing the residual gas phase.
Nevertheless, the reliability of known methods can be improved insofar as, in those methods, it can be difficult for the pulley systems to maintain adequate yarn tension, and insofar as relatively high travel speeds of the yarns can be used, which can lead to certain yarns escaping from grooves in the conveyor pulleys.
In addition, it can be desirable to provide devices that enable the number of yarns that can be treated per unit time to be increased.
Also known are documents FR 1 564 841, US 2007/0099527, DE 94 21 895, EP 1 277 874, and DE 3 424 166, which describe fiber coating methods. Also known is Document FR 2 727 435, which describes a reactive chemical vapor deposition (CVD) method.
There thus exists a need to provide devices enabling the reliability of methods for coating one or more yarns by vapor deposition to be improved.
There also exists a need to provide devices enabling the number of yarns that can be treated per unit time to be increased.